Positive resist composition and patterning process

ABSTRACT

A positive resist composition comprising a polymer having a tetrahydrobenzocycloheptane-substituted secondary or tertiary carboxyl group ester as an acid labile group exhibits a high contrast of alkaline dissolution rate before and after exposure, a high resolution, a good pattern profile and minimal edge roughness after exposure, a significant effect of suppressing acid diffusion rate, and improved etching resistance.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2010-002679 filed in Japan on Jan. 8, 2010,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a positive resist composition, and moreparticularly to a chemically amplified positive resist compositioncomprising a specific polymer; and a patterning process using the same.

BACKGROUND ART

To meet the demand for higher integration density and operating speed ofLSIs, the effort to reduce the pattern rule is in rapid progress. Thewide-spreading flash memory market and the demand for increased storagecapacities drive forward the miniaturization technology. As the advancedminiaturization technology, manufacturing of microelectronic devices atthe 65-nm node by the ArF lithography has been implemented in a massscale. Manufacturing of 45-nm node devices by the next generation ArFimmersion lithography is approaching to the verge of high-volumeapplication. The candidates for the next generation 32-nm node includeultra-high NA lens immersion lithography using a liquid having a higherrefractive index than water in combination with a high refractive indexlens and a high refractive index resist film, extreme ultraviolet (EUV)lithography of 13.5 nm wavelength, and double patterning version of theArF lithography, on which active research efforts have been made.

With respect to high-energy radiation of very short wavelength such aselectron beam (EB) or x-ray, hydrocarbons and similar light elementsused in resist materials have little absorption. Then polyhydroxystyrenebase resist materials are under consideration. Resist materials for EBlithography are practically used in the mask image writing application.Recently, the mask manufacturing technology becomes of greater interest.Reduction projection exposure systems or steppers have been used sincethe time when the exposure light was g-line. While their demagnificationfactor was ⅕, a factor of ¼ is now used as a result of chip sizeenlargement and projection lens diameter increase. It becomes of concernthat a dimensional error of a mask has an impact on the dimensionalvariation of a pattern on wafer. It is pointed out that as the patternfeature is reduced, the value of a dimensional variation on the waferbecomes greater than the value of a dimensional error of the mask. Thisis evaluated by a mask error enhancement factor (MEEF) which is adimensional variation on wafer divided by a dimensional error of mask.Patterns on the order of 45 nm often show an MEEF in excess of 4. In asituation including a demagnification factor of ¼ and a MEEF of 4, themask manufacture needs an accuracy substantially equivalent to that forequi-magnification masks.

The exposure system for mask manufacturing made a transition from thelaser beam exposure system to the EB exposure system to increase theaccuracy of line width. Since a further size reduction becomes possibleby increasing the accelerating voltage of the electron gun in the EBexposure system, the accelerating voltage increased from 10 keV to 30keV and reached 50 keV in the current mainstream system, with a voltageof 100 keV being under investigation.

As the accelerating voltage increases, a lowering of sensitivity ofresist film becomes of concern. As the accelerating voltage increases,the influence of forward scattering in a resist film becomes so reducedthat the contrast of electron image writing energy is improved toameliorate resolution and dimensional control whereas electrons can passstraightforward through the resist film so that the resist film becomesless sensitive. Since the mask exposure tool is designed for exposure bydirect continuous writing, a lowering of sensitivity of resist filmleads to an undesirably reduced throughput. Due to a need for highersensitivity, chemically amplified resist compositions are contemplated.

Thinning of resist film is in progress to facilitate reduction ofpattern feature in the EB lithography for mask manufacturing and toprevent the pattern from collapsing due to a higher aspect ratio duringdevelopment. In the case of photolithography, a thinning of resist filmgreatly contributes to resolution improvement. This is becauseintroduction of chemical mechanical polishing (CMP) or the like hasdriven forward device planarization. In the case of mask manufacture,substrates are flat, and the thickness of processable substrates (e.g.,Cr, MoSi or SiO₂) is predetermined by a percent light shield or phaseshift control. The dry etch resistance of resist film must be improvedbefore the film can be reduced in thickness.

It is generally believed that there is a correlation between the carbondensity and the dry etching resistance of resist film. For EB writingwhich is not affected by absorption, resist materials based on novolacresins having better etching resistance have been developed. Indenecopolymers described in JP 3865048 and acenaphthylene copolymersdescribed in JP-A 2006-169302 are expected to have improved etchingresistance due to a high carbon density and a robust main chainstructure based on cycloolefin structure.

Also, with respect to the soft x-ray (EUV) lithography at wavelength5-20 nm, the reduced absorption of carbon atoms was reported. Increasingthe carbon density is effective not only for improving dry etchingresistance, but also for increasing the transmittance in the soft x-raywavelength region.

As the feature size is reduced, image blurs due to acid diffusion becomea problem. To insure resolution for fine patterns with a size of 45 nmet seq., not only an improvement in dissolution contrast is requisite,but control of acid diffusion is also important, as known from previousreports. Since chemically amplified resist compositions are designedsuch that sensitivity and contrast are enhanced by acid diffusion, anattempt to minimize acid diffusion by reducing the temperature and/ortime of post-exposure baking (PEB) fails, resulting in drasticreductions of sensitivity and contrast. Since the distance of aciddiffusion is closely related to the type of acid labile group, it wouldbe desirable to have an acid labile group which permits deprotectionreaction to proceed at a very short distance of acid diffusion.

In JP-A 2007-171895, methacrylates having an indane, acenaphthene,fluorene or 9,10-dihydroanthracene pendant are exemplified as themonomer to form a copolymer for use in photoresist underlayer formingmaterial. Acid labile groups in the form of indane ortetrahydronaphthalene (meth)acrylate are proposed. Inclusion of aromaticwithin the acid labile group improves etch resistance and EUVtransmittance. JP-A 2007-279699 discloses a resist material comprising acopolymer of hydroxystyrene wherein an ester bond moiety is secondary ortertiary. In particular, the secondary ester bond moiety has a reducedsteric free volume, permitting deprotection reaction to proceed withshort acid diffusion. However, indane and tetrahydronaphthalene are notfully dissolution inhibitory, inviting film slimming of a developedpattern and failing to provide a satisfactory resolution.

A tradeoff among sensitivity, edge roughness and resolution is reported.Increasing sensitivity leads to reductions of edge roughness andresolution. Controlling acid diffusion improves resolution at thesacrifice of edge roughness and sensitivity. Addition of an acidgenerator capable of generating a bulky acid is effective forsuppressing acid diffusion, but leads to reductions of edge roughnessand sensitivity. It is then proposed to copolymerize a polymer with anacid generator in the form of an onium salt having polymerizable olefin.JP-A 2006-178317 discloses polymer-bound sulfonium salts havingpolymerizable olefin capable of generating a sulfonic acid and similariodonium salts. A photoresist using a base polymer having apolymerizable acid generator copolymerized therein exhibits reduced edgeroughness due to controlled acid diffusion and uniform dispersion ofacid generator within the polymer, succeeding in improving bothresolution and edge roughness at the same time.

CITATION LIST

Patent Document 1: JP 3865048

Patent Document 2: JP-A 2006-169302

Patent Document 3: JP-A 2007-171895

Patent Document 4: JP-A 2007-279699

Patent Document 5: JP-A 2006-178317

DISCLOSURE OF INVENTION

An object of the present invention is to provide a positive resistcomposition, typically chemically amplified positive resist composition,comprising a specific polymer, which exhibits a high resolutionsurpassing prior art positive resist compositions, and forms a resistfilm having a minimal edge roughness (LER or LWR), a good patternprofile after exposure, and improved etching resistance. Another objectis to provide a pattern forming process using the same.

Making investigations to seek for a positive resist composition whichexhibits a high resolution, a minimal edge roughness (LER or LWR), agood pattern profile after exposure, and improved etching resistance,the inventors have found that better results are obtained when a polymercomprising recurring units having atetrahydrobenzocycloheptane-substituted secondary or tertiary carboxylgroup ester, specifically selected from (meth)acrylic acid andderivatives thereof, styrenecarboxylic acid, andvinylnaphthalenecarboxylic acid, is used as a base resin to formulate apositive resist composition, typically chemically amplified positiveresist composition.

The above polymer is used as a base resin to formulate a positive resistcomposition, typically chemically amplified positive resist compositionin order to suppress acid diffusion for improving dissolution contrastand etching resistance. The positive resist composition, typicallychemically amplified positive resist composition exhibits a remarkablyhigh contrast of alkaline dissolution rate before and after exposure, asignificant effect of suppressing acid diffusion, a high resolution, agood pattern profile and minimal edge roughness after exposure, andimproved etching resistance, and is suited as a fine pattern-formingmaterial for the fabrication of VLSIs or photomasks.

The positive resist composition of the invention forms a resist filmwhich exhibits a high dissolution contrast, a significant effect ofsuppressing acid diffusion, a high resolution, a good exposure latitude,process adaptability, a good pattern profile after exposure, andimproved etching resistance. By virtue of these advantages, thecomposition is fully useful in commercial application and suited as apattern-forming material for the fabrication of VLSIs and photomasks.

In one aspect, the invention provides a positive resist compositioncomprising as a base resin a polymer having carboxyl groups whosehydrogen is substituted by an acid labile group having the generalformula (1).

Herein W is an ethylene, propylene, butylene or pentylene group whichbonds at opposite ends to carbon atoms C_(A) and C_(B); R¹ is hydrogenor a straight, branched or cyclic C₁-C₆ alkyl group, which bonds to acarbon atom in W, with the proviso that R¹ is not hydrogen when W isethylene or propylene; m is an integer of 1 to 4, with the proviso thatwhen m is 2 or more, R¹ may be the same or different and R¹ may bondtogether to form a C₃-C₉ ring with a carbon atom in W; R² is selectedfrom the class consisting of C₁-C₄ alkyl, alkoxy, alkanoyl,alkoxycarbonyl, hydroxyl, nitro, C₆-C₁₀, aryl, halogen, and cyano; n isan integer of 1 to 4; and R is hydrogen or a straight, branched orcyclic C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl or C₆-C₁₀ aryl groupwhich may have an oxygen or sulfur atom.

In a preferred embodiment, the resist composition comprises as the baseresin a polymer comprising recurring units (a) of the general formula(2), selected from (meth)acrylic acid and derivatives thereof,styrenecarboxylic acid, and vinylnaphthalenecarboxylic acid, each havingsubstituted thereon an acid labile group of formula (1), the polymerhaving a weight average molecular weight of 1,000 to 500,000.

Herein W, R¹, R², R, C_(A), C_(B), m, and n are as defined above, X¹ isa single bond, —C(═O)—O—R⁴—, phenylene or naphthylene group, R⁴ is astraight, branched or cyclic C₁-C₁₀ alkylene group which may have anester group, ether group or lactone ring, and R³ is hydrogen or methyl.

In a preferred embodiment, the polymer is a copolymer comprisingrecurring units (a) of the general formula (2), selected from(meth)acrylic acid and derivatives thereof, styrenecarboxylic acid, andvinylnaphthalenecarboxylic acid, each having substituted thereon an acidlabile group of formula (1), and recurring units (b) having an adhesivegroup selected from the class consisting of hydroxyl, lactone, ether,ester, carbonyl, and cyano groups, molar fractions “a” and “b” of therespective units being in the range: 0<a<1.0, 0<b<1.0, and 0.05≦a+b≦1.0,the copolymer having a weight average molecular weight of 1,000 to500,000.

Typically the recurring units (b) are recurring units having a phenolichydroxyl group. The recurring units having a phenolic hydroxyl group arepreferably selected from units (b1) to (b8) represented by the generalformula (3).

Herein X² and X³ each are a single bond or —C(═O)—O—R⁶—, X⁴ and X⁵ eachare —C(═O)—O—R⁶—, R⁶ is a single bond or a straight, branched or cyclicC₁-C₁₀alkylene group, R⁵ is each independently hydrogen or methyl, Y¹and Y² each are methylene or ethylene, Z is methylene, oxygen or sulfur,and p is 1 or 2.

In a preferred embodiment, the copolymer has further copolymerizedtherein recurring units selected from units (c1) to (c5) of indene,acenaphthylene, chromone, coumarin, and norbornadiene, or derivativesthereof, represented by the general formula (4).

Herein R⁹ to R¹³ are each independently selected from the classconsisting of hydrogen, C₁-C₃₀ alkyl, partially or entirelyhalo-substituted alkyl, alkoxy, alkanoyl or alkoxycarbonyl group, C₆-C₁₀aryl group, halogen, and 1,1,1,3,3,3-hexafluoro-2-propanol, and Z ismethylene, oxygen or sulfur.

In a preferred embodiment, the copolymer has further copolymerizedtherein units selected from sulfonium salts (d1) to (d3) represented bythe general formula (5).

Herein R²⁰, R²⁴, and R²⁸ each are hydrogen or methyl, R²¹ is a singlebond, phenylene, —O—R³³—, or —C(═O)—Y—R³³—, Y is oxygen or NH, R³³ is astraight, branched or cyclic C₁-C₆ alkylene group, alkenylene orphenylene group, which may contain a carbonyl, ester, ether or hydroxylgroup, R²², R²³, R²⁵, R²⁶, R²⁷, R²⁹, R³⁰, and R³¹ are each independentlya straight, branched or cyclic C₁-C₁₂ alkyl group which may contain acarbonyl, ester or ether group, or a C₆-C₁₂ aryl, C₇-C₂₀ aralkyl, orthiophenyl group, Z₀ is a single bond, methylene, ethylene, phenylene,fluorophenylene, —O—R³²—, or —C(═O)—Z₁—R³²—, Z₁ is oxygen or NH, R³² isa straight, branched or cyclic C₁-C₆ alkylene group, alkenylene orphenylene group, which may contain a carbonyl, ester, ether or hydroxylradical, M⁻ is a non-nucleophilic counter ion, d1, d2 and d3 are in therange of 0≦d1≦0.3, 0≦d2≦0.3, 0≦d3≦0.3, and 0<d1+d2+d3≦0.3.

The resist composition may further comprise an organic solvent and anacid generator. Then the composition is a chemically amplified positiveresist composition. The resist composition may further comprise adissolution regulator, a basic compound and/or a surfactant as anadditive.

In another aspect, the invention provides a pattern forming processcomprising the steps of applying the positive resist composition definedabove onto a substrate to form a coating, heat treating and exposing thecoating to high-energy radiation, and developing the exposed coatingwith a developer.

The positive resist composition, typically chemically amplified positiveresist composition, is used not only in the lithography for formingsemiconductor circuits, but also in the formation of mask circuitpatterns, micromachines, and thin-film magnetic head circuits.

ADVANTAGEOUS EFFECTS OF INVENTION

The positive resist composition exhibits a remarkably high contrast ofalkaline dissolution rate before and after exposure, a high resolution,a good pattern profile and minimal edge roughness (LER or LWR) afterexposure, a significant effect of suppressing acid diffusion rate, andimproved etching resistance. The composition is thus suited as a finepattern-forming material for the fabrication of VLSIs or photomasks anda pattern-forming material for EUV lithography.

DESCRIPTION OF EMBODIMENTS

The singular forms “a,” “an” and “the” include plural referents unlessthe context clearly dictates otherwise. “Optional” or “optionally” meansthat the subsequently described event or circumstances may or may notoccur, and that description includes instances where the event orcircumstance occurs and instances where it does not.

As used herein, the terminology “(meth)acrylic acid” or “(meth)acrylate”refers collectively to acrylic and methacrylic acid or acrylate andmethacrylate. The terminology “C_(x)-C_(y)”, as applied to a particularunit, such as, for example, a chemical compound or a chemicalsubstituent group, means having a carbon atom content of from “x” carbonatoms to “y” carbon atoms per such unit.

The acronyms LER and LWR are line edge roughness and line widthroughness, respectively, and PEB stands for post-exposure baking.

The invention provides a positive resist composition comprising as abase resin a polymer or high-molecular-weight compound having carboxylgroups whose hydrogen is substituted at least by an acid labile grouphaving the general formula (1).

Herein W is an ethylene, propylene, butylene or pentylene group whichbonds at opposite ends to carbon atoms C_(A) and C₈. R¹ is hydrogen or astraight, branched or cyclic C₁-C₆ alkyl group, which bonds to a carbonatom in W. R¹ is not hydrogen when W is ethylene or propylene. Thesubscript m is an integer of 1 to 4. When m is 2 or more, R¹ may be thesame or different and two R¹ groups may bond together to form a C₁-C₉ring with a carbon atom(s) in W. R² is selected from among C₁-C₄ alkyl,alkoxy, alkanoyl, alkoxycarbonyl, hydroxyl, nitro, C₆-C₁₀ aryl, halogen,and cyano groups, and n is an integer of 1 to 4. R is hydrogen or astraight, branched or cyclic C₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂alkynyl or C₆-C₁₀ aryl group which may have an oxygen or sulfur atom.

Examples of R¹ include hydrogen, methyl, ethyl, propyl, butyl,cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. When two R¹ groupsbond together to form a ring, examples include cyclopropyl, cyclobutyl,cyclopentyl and cyclohexyl, and they may form a Spiro ring with theC_(A)—W—C_(B)—C ring. When W is ethylene or propylene, dissolutioninhibition and elimination reaction are not sufficient, and in thiscase, an alkyl as R¹ is attached to W, so that the stability ofcarbocation of C_(A) carbon increases in the intermediate stage ofdeprotection reaction, whereby the deprotection reaction is improved inreactivity. The attachment of alkyl as R¹ also improves dissolutioninhibition at the same time, achieving an improvement in dissolutioncontrast. When W is butylene or pentylene, the ring is so improved inflexibility that there is an increased likelihood for reaction such asformation of carbocation or formation of olefin to take place uponelimination. An improvement in dissolution inhibitory function due to anincreased carbon count is expectable.

Examples of R² include hydrogen, methyl, ethyl, propyl, butyl, methoxy,ethoxy, acetoxy, and methoxycarbonyl, with hydrogen, methyl, methoxy,acetoxy and methoxycarbonyl being preferred.

In a preferred embodiment, the acid labile group of formula (1)substitutes for hydrogen atom of the carboxyl group on (meth)acrylicacid and derivatives thereof, styrenecarboxylic acid, andvinylnaphthalenecarboxylic acid. It is noted that (meth)acrylic acid andderivatives thereof are collectively referred to as (meth)acrylates,hereinafter. Specifically, a polymer comprising recurring units (a) ofthe general formula (2) and having a weight average molecular weight(Mw) of 1,000 to 500,000 is used as the base resin.

Herein W, R¹, R², R, C_(A), C_(B), m, and n are as defined above, X¹ isa single bond, —C(═O)—O—R⁴—, phenylene or naphthylene group, R⁴ is astraight, branched or cyclic C₁-C₁₀ alkylene group which may have anester group (—COO—), ether group (—O—) or lactone ring, and R³ ishydrogen or methyl. Typical of the C₁-C₁₀ alkylene group having lactonering is a group of the formula below.

Specifically, the recurring units (a) of formula (2) include units (a1)to (a4) represented by the general formula (6).

Herein, W, R¹ to R³, R, C_(A), C_(B), m, and n are as defined above, R⁷is a straight, branched or cyclic C₁-C₁₀ alkylene group which may havean ester group, ether group or lactone ring, and 0<a1+a2+a3+a4<1.0. Inparticular, these acid labile groups are applicable to the KrF, EB andEUV lithography.

As compared with the 5- or 6-membered ring wherein C_(A) and C_(B) arelinked by ethylene or propylene, the 5- or 6-membered ring having alkylattached thereto leads to an improved contrast due to improvedreactivity of deprotection and improved dissolution inhibitory functionat the same time. As compared with the 5- or 6-membered ring, the 7- or8-membered ring wherein C_(A) and C_(B) are linked by butylene orpentylene leads to an improved dissolution contrast. In the case of 9-or more-membered rings, monomer synthesis is difficult, and fatsolubility is so high that pattern collapse may occur due to swellingduring development.

Examples of suitable monomers from which recurring units (a1) to (a4)are derived are shown below.

The polymerizable, acid-labile ester compounds from which recurringunits (a1) are derived may be prepared from reaction of2-alkyl-1-indanol, 1,2,3,4-tetrahydro-2-alkyl-1-naphthol,benzocycloheptanol and benzocyclooctanol with methacrylic acid chloride.The ester compounds from which other recurring units (a2) to (a4) arederived may be similarly prepared.

In a preferred embodiment, the polymer having acid labile groups offormula (1) is a copolymer comprising recurring units (a) of the generalformula (2), selected from (meth)acrylates, styrenecarboxylic acid, andvinylnaphthalenecarboxylic acid, and recurring units (b) having anadhesive group selected from among hydroxyl, lactone, ether, ester,carbonyl, and cyano groups. More preferably, the recurring units (b) arerecurring units having a phenolic hydroxyl group because the group has asensitizing effect in the EB and EUV lithography. The recurring unitshaving a phenolic hydroxyl group are preferably selected from units (b1)to (b8) represented by the general formula (3).

Herein X² and X³ each are a single bond or —C(═O)—O—R⁶—, X⁴ and X⁵ eachare —C(═O)—O—R⁶—, R⁶ is a single bond or a straight, branched or cyclicC₁-C₁₀ alkylene group, R⁵ is each independently hydrogen or methyl, Y¹and Y² each are methylene or ethylene, Z is methylene, oxygen or sulfur,and p is 1 or 2.

Examples of suitable monomers from which the recurring units (b1) to(b8) having a phenolic hydroxyl group are derived are given below.

Examples of suitable monomers from which the recurring units (b) havingan adhesive group selected from among non-phenolic hydroxyl group,lactone ring, ether group, ester group, carbonyl group, cyano group,cyclic —O—C(═O)—S— and —O—C(═O)—NH— are derived are given below.

In the case of a monomer having a hydroxyl group, the hydroxyl group maybe replaced by an acetal group susceptible to deprotection with acid,typically ethoxyethoxy, prior to polymerization, and the polymerizationbe followed by deprotection with weak acid and water. Alternatively, thehydroxy group may be replaced by an acetyl, formyl, pivaloyl or similargroup prior to polymerization, and the polymerization be followed byalkaline hydrolysis.

In a more preferred embodiment, the copolymer has further copolymerizedtherein recurring units selected from units (c1) to (c5) of indene,acenaphthylene, chromone, coumarin, and norbornadiene, or derivativesthereof, represented by the general formula (4).

Herein R⁹ to R¹³ are each independently hydrogen, a C₁-C₃₀ alkyl,haloalkyl, alkoxy, alkanoyl or alkoxycarbonyl group, C₁-C₁₀ aryl group,halogen, or 1,1,1,3,3,3-hexafluoro-2-propanol group, and Z is methylene,oxygen or sulfur. As used herein, the term “haloalkyl” refers to alkylin which some or all hydrogen atoms are substituted by halogen.

Examples of suitable monomers from which units (c1) to (c5) of indene,acenaphthylene, chromone, coumarin, and norbornadiene derivatives arederived are given below.

In a further embodiment, an acid generator (d) in the form of an oniumsalt having polymerizable olefin may be copolymerized with the foregoingmonomers.

In this embodiment, the copolymer may have further copolymerized thereinrecurring units having a sulfonium salt (d1) to (d3) represented by thegeneral formula (5).

Herein R²⁰, R²⁴ and R²⁸ each are hydrogen or methyl. R²¹ is a singlebond, phenylene, —O—R³³—, or —C(═O)—Y—R³³— wherein Y is oxygen or NH andR³³ is a straight, branched or cyclic C₁-C₆ alkylene group, alkenylenegroup or phenylene group, which may contain a carbonyl (—CO—), ester(—COO—), ether (—O—) or hydroxyl group. R²², R²³, R²⁵, R²⁶, R²⁷, R²⁹,R³⁰, and R³¹ are each independently a straight, branched or cyclicC₁-C₁₂ alkyl group which may contain a carbonyl, ester or ether group,or a C₆-C₁₂ aryl group, C₇-C₂₀ aralkyl group, or thiophenyl group. Z₀ isa single bond, methylene, ethylene, phenylene, fluorinated phenylene,—O—R³²—, or —C(═O)—Z₁—R³²— wherein Z₁ is oxygen or NH and R³² is astraight, branched or cyclic C₁-C₆ alkylene group, alkenylene group orphenylene group, which may contain a carbonyl, ester, ether or hydroxylgroup. M⁻ is a non-nucleophilic counter ion. Molar fractions d1 to d3are in the range: 0≦d1≦0.3, 0≦d2≦0.3, 0≦d3≦0.3, and 0≦d1+d2+d3≦0.3.

Examples of the non-nucleophilic counter ion represented by M⁻ includehalide ions such as chloride and bromide ions; fluoroalkylsulfonate ionssuch as triflate, 1,1,1-trifluoroethanesulfonate, andnonafluorobutanesulfonate; arylsulfonate ions such as tosylate,benzenesulfonate, 4-fluorobenzenesulfonate, and1,2,3,4,5-pentafluorobenzenesulfonate; alkylsulfonate ions such asmesylate and butanesulfonate; imidates such asbis(trifluoromethylsulfonyl)imide, bis(perfluoroethylsulfonyl)imide andbis(perfluorobutylsulfonyl)imide; methidates such astris(trifluoromethylsulfonyl)methide andtris(perfluoroethylsulfonyl)methide.

The attachment of an acid generator to the polymer main chain iseffective in restraining acid diffusion, thereby preventing a reductionof resolution due to blur by acid diffusion. Also edge roughness (LER orLWR) is improved since the acid generator is uniformly diffused.

While the polymer according to the invention comprises recurring units(a) as essential units, it may have additionally copolymerized thereinrecurring units (e) of (meth)acrylate having substituted thereon an acidlabile group R¹⁵ and/or recurring units (f) of hydroxystyrene havingsubstituted thereon an acid labile group R¹⁷, as represented by thefollowing general formula (7).

Herein R¹⁴ and R¹⁶ each are hydrogen or methyl, R¹⁵ and R¹⁷ each are anacid labile group other than formula (1), and q is 1 or 2.

Besides the recurring units (a) to (f), additional recurring units (g)may be copolymerized in the polymer, which include recurring unitsderived from styrene, vinylnaphthalene, vinylanthracene, vinylpyrene,methyleneindane, and the like.

The acid labile group represented by R¹⁵ and R¹⁷ in formula (7) may beselected from a variety of such groups. The acid labile groups may bethe same or different and preferably include groups of the followingformulae (A-1) to (A-3).

In formula (A-1), R^(L30) is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in whicheach alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (A-3). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl, 1-ethylcyclopentyl,1-butylcyclopentyl, 1-ethylcyclohexyl, 1-butylcyclohexyl,1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl, and2-methyl-2-adamantyl. Exemplary trialkylsilyl groups are trimethylsilyl,triethylsilyl, and dimethyl-tert-butylsilyl. Exemplary oxoalkyl groupsare 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl, and5-methyl-2-oxooxolan-5-yl. Letter A1 is an integer of 0 to 6.

In formula (A-2), R^(L31) and R^(L32) are hydrogen or straight, branchedor cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms. Exemplary alkyl groups include methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl,2-ethylhexyl, and n-octyl. R^(L33) is a monovalent hydrocarbon group of1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, which may containa heteroatom such as oxygen, examples of which include straight,branched or cyclic alkyl groups and substituted forms of such alkylgroups in which some hydrogen atoms are replaced by hydroxyl, alkoxy,oxo, amino, alkylamino or the like. Illustrative examples of thesubstituted alkyl groups are shown below.

A pair of R^(L31) and R^(L32), R^(L31) and R^(L33), or, R^(L32) andR^(L33) may bond together to form a ring with the carbon and oxygenatoms to which they are attached. Each of R^(L31), R^(L32) and R^(L33)is a straight or branched alkylene group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms when they form a ring, while the ringpreferably has 3 to 10 carbon atoms, more preferably 4 to 10 carbonatoms.

Examples of the acid labile groups of formula (A-1) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Also included are substituent groups having the formulae (A-1)-1 to(A-1)-10.

Herein R^(L37) is each independently a straight, branched or cyclicC₁-C₁₀ alkyl group or C₆-C₂₀ aryl group, R^(L38) is hydrogen or astraight, branched or cyclic C₁-C₁₀ alkyl group, R^(L39) is eachindependently a straight, branched or cyclic C₂-C_(n) alkyl group orC₆-C₂₀ aryl group, and A1 is as defined above.

Of the acid labile groups of formula (A-2), the straight and branchedones are exemplified by the following groups having formulae (A-2)-1 to(A-2)-35.

Of the acid labile groups of formula (A-2), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Other examples of acid labile groups include those of the followingformula (A-2a) or (A-2b) while the polymer may be crosslinked within themolecule or between molecules with these acid labile groups.

Herein R^(L40) and R^(L41) each are hydrogen or a straight, branched orcyclic C₁-C₈ alkyl group, or R^(L40) and R^(L41), taken together, mayform a ring with the carbon atom to which they are attached, and R^(L40)and R^(L41) are straight or branched C₁-C₈ alkylene groups when theyform a ring. R^(L42) is a straight, branched or cyclic C₁-C₁₀ alkylenegroup. Each of B1 and D1 is 0 or an integer of 1 to 10, preferably 0 oran integer of 1 to 5, and C1 is an integer of 1 to 7. “A” is a(C1+1)-valent aliphatic or alicyclic saturated hydrocarbon group,aromatic hydrocarbon group or heterocyclic group having 1 to 50 carbonatoms, which may be separated by a heteroatom or in which some of thehydrogen atoms attached to carbon atoms may be substituted by hydroxyl,carboxyl, carbonyl groups or fluorine atoms. “B” is —CO—O—, —NHCO—O— or—NHCONH—. Preferably, “A” is selected from divalent to tetravalent,straight, branched or cyclic C₁-C₂₀ alkylene, alkyltriyl andalkyltetrayl groups, and C₆-C₃₀arylene groups, which may contain aheteroatom or in which some of the hydrogen atoms attached to carbonatoms may be substituted by hydroxyl, carboxyl, acyl groups or halogenatoms. The subscript C1 is preferably an integer of 1 to 3.

The crosslinking acetal groups of formulae (A-2a) and (A-2b) areexemplified by the following formulae (A-2)-36 through (A-2)-43.

In formula (A-3), R^(L34), R^(L35) and R^(L36) each are a monovalenthydrocarbon group, typically a straight, branched or cyclic C₁-C₂₀ alkylgroup, which may contain a heteroatom such as oxygen, sulfur, nitrogenor fluorine. A pair of R^(L34) and R^(L35), R^(L34) and R^(L36), orR^(L35) and R^(L36) may bond together to form a C₃-C₂₀ ring with thecarbon atom to which they are attached.

Exemplary tertiary alkyl groups of formula (A-3) include tert-butyl,triethylcarbyl, 1-ethylnorbornyl, 1-methylcyclohexyl,1-ethylcyclopentyl, 2-(2-methyl)adamantyl, 2-(2-ethyl)adamantyl, andtert-amyl.

Other exemplary tertiary alkyl groups include those of the followingformulae (A-3)-1 to (A-3)-18.

Herein R^(L43) is each independently a straight, branched or cyclicC₁-C₈ alkyl group or C₆-C₂₀ aryl group, typically phenyl or naphthyl,R^(L44) and R^(L46) each are hydrogen or a straight, branched or cyclicC₁-C₂₀ alkyl group, and R^(L45) is a C₆-C₂₀ aryl group, typicallyphenyl.

The polymer may be crosslinked within the molecule or between moleculeswith groups having R^(L47) which is a di- or multi-valent alkylene orarylene group, as shown by the following formulae (A-3)-19 and (A-3)-20.

Herein R^(L43) is as defined above, R^(L47) is a straight, branched orcyclic C₁-C₂₀ alkylene group or arylene group, typically phenylene,which may contain a heteroatom such as oxygen, sulfur or nitrogen, andE1 is an integer of 1 to 3.

Of recurring units having acid labile groups of formula (A-3), recurringunits of (meth)acrylate having an exo-form structure represented by theformula (A-3)-21 are preferred.

Herein, R¹⁴ is as defined above; R^(c3) is a straight, branched orcyclic C₁-C₈ alkyl group or an optionally substituted C₆-C₂₀ aryl group;R^(c4) to R^(c9), R^(c12) and R^(c13) are each independently hydrogen ora monovalent C₁-C₁₅ hydrocarbon group which may contain a heteroatom;and R^(c10) and R^(c11) are hydrogen or a monovalent C₁-C₁₅ hydrocarbongroup which may contain a heteroatom. Alternatively, a pair of R^(c4)and R^(c5), R^(c6) and R^(c8), R^(c6) and R^(c9), R^(c7) and R^(c9),R^(c7) and R^(c13), R^(c8) and R^(c12), R^(c10) and R^(c11), or R^(c11)and R^(c12), taken together, may form a ring, and in that event, eachring-forming R is a divalent C₁-C₁₅ hydrocarbon group which may containa heteroatom. Also, a pair of R^(c4) and R^(c13), R^(c10) and R^(c13),or R^(c6) and R^(c8) which are attached to vicinal carbon atoms may bondtogether directly to form a double bond. The formula also represents anenantiomer.

The ester form monomers from which recurring units having an exo-formstructure represented by formula (A-3)-21 are derived are described inU.S. Pat. No. 6,448,420 (JP-A 2000-327633). Illustrative non-limitingexamples of suitable monomers are given below.

Also included in the acid labile groups of formula (A-3) are acid labilegroups of (meth)acrylate having furandiyl, tetrahydrofurandiyl oroxanorbornanediyl as represented by the following formula (A-3)-22.

Herein, R¹⁴ is as defined above; R^(c14) and R^(c15) are eachindependently a monovalent, straight, branched or cyclic C₁-C₁₀hydrocarbon group, or R^(c14) and R^(c15), taken together, may form analiphatic hydrocarbon ring with the carbon atom to which they areattached. R^(c16) is a divalent group selected from furandiyl,tetrahydrofurandiyl and oxanorbornanediyl. R^(c17) is hydrogen or amonovalent, straight, branched or cyclic C₁-C₁₀ hydrocarbon group whichmay contain a heteroatom.

Examples of the monomers from which the recurring units substituted withacid labile groups having furandiyl, tetrahydrofurandiyl andoxanorbornanediyl are derived are shown below. Note that Me is methyland Ac is acetyl.

The polymer used herein may be synthesized by any desired methods, forexample, by dissolving one or more monomers selected from the monomersto form the recurring units (a) to (g) in an organic solvent, adding aradical polymerization initiator thereto, and effecting heatpolymerization. Examples of the organic solvent which can be used forpolymerization include toluene, benzene, tetrahydrofuran, diethyl etherand dioxane. Examples of the polymerization initiator used hereininclude 2,2′-azobisisobutyronitrile (AIM),2,2′1-azobis(2,4-dimethylvaleronitrile), dimethyl2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide.Preferably the system is heated at 50 to 80° C. for polymerization totake place. The reaction time is 2 to 100 hours, preferably 5 to 20hours.

When hydroxystyrene or hydroxyvinylnaphthalene is copolymerized, analternative method is possible. Specifically, acetoxystyrene oracetoxyvinylnaphthalene is used instead of hydroxystyrene orhydroxyvinylnaphthalene, and after polymerization, the acetoxy group isdeprotected by alkaline hydrolysis as mentioned above, for therebyconverting the polymer product to polyhydroxystyrene orhydroxypolyvinylnaphthalene. For alkaline hydrolysis, a base such asaqueous ammonia or triethylamine may be used. The reaction temperatureis −20° C. to 100° C., preferably 0° C. to 60° C., and the reaction timeis 0.2 to 100 hours, preferably 0.5 to 20 hours.

In the copolymer, recurring units (a) to (g) may be incorporated in thefollowing molar fraction:

0<a<1.0, preferably 0.05≦a≦0.8, and more preferably 0.08≦a≦≦0.7;0<b<1.0, preferably 0.1≦b≦0.9, and more preferably 0.15≦b≦0.8;0≦c<1.0, preferably 0≦c≦0.9, and more preferably 0≦c≦0.8;0≦d≦0.5, preferably 0≦d≦0.4, and more preferably 0≦d≦0.3;

-   0≦e≦0.5, preferably 0≦e≦0.4, and more preferably 0≦e≦0.3;-   0≦f≦0.5, preferably 0≦f≦0.4, and more preferably 0≦f≦0.3;-   0≦g≦0.5, preferably 0≦g≦0.4, and more preferably 0≦g≦0.3;

preferably 0.2≦a+b+c≦1.0, more preferably 0.3≦a+b+c≦1.0; anda+b+c+d+e+f+g=1.

The meaning of a+b+c=1, for example, is that in a polymer comprisingrecurring units (a), (b), and (c), the sum of recurring units (a), (b),and (c) is 100 mol % based on the total amount of entire recurringunits. The meaning of a+b+c<1 is that the sum of recurring units (a),(b), and (c) is less than 100 mol % based on the total amount of entirerecurring units, indicating the inclusion of other recurring units.

The polymer serving as the base resin in the resist composition shouldpreferably have a weight average molecular weight (Mw) in the range of1,000 to 500,000, and more preferably 2,000 to 30,000, as measured bygel permeation chromatography (GPC) versus polystyrene standards usingtetrahydrofuran as a solvent. With too low a Mw, the resist compositionmay become less heat resistant. A polymer with too high a Mw may losealkaline solubility and give rise to a footing phenomenon after patternformation.

If a polymer has a wide molecular weight distribution or dispersity(Mw/Mn), which indicates the presence of lower and higher molecularweight polymer fractions, there is a possibility that foreign matter isleft on the pattern or the pattern profile is degraded. The influencesof molecular weight and dispersity become stronger as the pattern rulebecomes finer. Therefore, the multi-component copolymer shouldpreferably have a narrow dispersity (Mw/Mn) of 1.0 to 2.0, especially1.0 to 1.5, in order to provide a resist composition suitable formicropatterning to a small feature size.

It is understood that a blend of two or more polymers which differ incompositional ratio, molecular weight or dispersity is acceptable.

The polymer is advantageously used as a base resin in a positive resistcomposition, typically chemically amplified positive resist composition.Specifically, the polymer is used as a base resin and combined with anydesired components including an organic solvent, acid generator,dissolution regulator, basic compound, and surfactant to formulate apositive resist composition. This positive resist composition has a veryhigh sensitivity in that the dissolution rate in developer of thepolymer in exposed areas is accelerated by catalytic reaction. Inaddition, the resist film has a high dissolution contrast, resolution,exposure latitude, and process adaptability, and provides a good patternprofile after exposure, yet better etching resistance, and minimalproximity bias because of restrained acid diffusion. By virtue of theseadvantages, the composition is fully useful in commercial applicationand suited as a pattern-forming material for the fabrication of VLSIs orphotomasks. Particularly when an acid generator is incorporated toformulate a chemically amplified positive resist composition capable ofutilizing acid catalyzed reaction, the composition has a highersensitivity and is further improved in the properties described above.

The positive resist composition may further comprise an organic solvent,basic compound, dissolution regulator, surfactant, and acetylenealcohol, alone or in combination.

Inclusion of a dissolution regulator may lead to an increased differencein dissolution rate between exposed and unexposed areas and a furtherimprovement in resolution. Addition of a basic compound may be effectivein suppressing the diffusion rate of acid in the resist film, achievinga further improvement in resolution. Addition of a surfactant mayimprove or control the coating characteristics of the resistcomposition.

The positive resist composition may include an acid generator in orderfor the composition to function as a chemically amplified positiveresist composition. Typical of the acid generator used herein is aphotoacid generator (PAG) capable of generating an acid in response toactinic light or radiation. It is any compound capable of generating anacid upon exposure to high-energy radiation. Suitable photoacidgenerators include sulfonium salts, iodonium salts,sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acidgenerators. The acid generators may be used alone or in admixture of twoor more. Exemplary acid generators are described in U.S. Pat. No.7,537,880 (JP-A 2008-111103, paragraphs [0122] to [0142]).

Examples of the organic solvent used herein are described in JP-A2008-111103, paragraphs [0144] to [0145] (U.S. Pat. No. 7,537,880).Specifically, exemplary solvents include ketones such as cyclohexanoneand methyl-2-n-amyl ketone; alcohols such as 3-methoxybutanol,3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether,ethylene glycol monomethyl ether, propylene glycol monoethyl ether,ethylene glycol monoethyl ether, propylene glycol dimethyl ether, anddiethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate (PGMEA), propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone, and mixtures thereof.Exemplary basic compounds are described in JP-A 2008-111103, paragraphs[0146] to [0164], for example, primary, secondary and tertiary aminecompounds, specifically amine compounds having a hydroxyl, ether, ester,lactone, cyano or sulfonate group. Exemplary surfactants are describedin JP-A 2008-111103, paragraphs [0165] to [0166]. Exemplary dissolutionregulators are described in JP-A 2008-122932 (US 2008090172), paragraphs[0155] to [0178], and exemplary acetylene alcohols in paragraphs [0179]to [0182]. Also useful are quenchers of polymer type as described inJP-A 2008-239918. The polymeric quencher segregates at the resistsurface after coating and thus enhances the rectangularity of resistpattern. When a protective film is applied as is often the case in theimmersion lithography, the polymeric quencher is also effective forpreventing slimming of resist pattern or rounding of pattern top.

An appropriate amount of the acid generator used is 0.01 to 100 parts,and preferably 0.1 to 80 parts. An appropriate amount of the organicsolvent used is 50 to 10,000 parts, especially 100 to 5,000 parts. Thedissolution regulator may be blended in an amount of 0 to 50 parts,preferably 0 to 40 parts, the basic compound in an amount of 0 to 100parts, preferably 0.001 to 50 parts, and the surfactant in an amount of0 to 10 parts, preferably 0.0001 to 5 parts. All amounts are expressedin parts by weight relative to 100 parts by weight of the base resin.

Process

The positive resist composition, typically chemically amplified positiveresist composition comprising a polymer having acid labile groups offormula (1), an acid generator, and a basic compound in an organicsolvent is used in the fabrication of various integrated circuits.Pattern formation using the resist composition may be performed bywell-known lithography processes. The process generally involvescoating, heat treatment (or prebaking), exposure, heat treatment (PEB),and development. If necessary, any additional steps may be added.

The positive resist composition is first applied onto a substrate onwhich an integrated circuit is to be formed (e.g., Si, SiO₂, SiN, SiON,TiN, WSi, BPSG, SOG, or organic antireflective coating) or a substrateon which a mask circuit is to be formed (e.g., Cr, CrO, CrON, MoSi, orSiO₂) by a suitable coating technique such as spin coating, rollcoating, flow coating, dip coating, spray coating or doctor coating. Thecoating is prebaked on a hot plate at a temperature of 60 to 150° C. for10 seconds to 30 minutes, preferably 80 to 120° C. for 30 seconds to 20minutes. The resulting resist film is generally 0.1 to 2.0 μm thick.

The resist film is then exposed to a desired pattern of high-energyradiation such as UV, deep-UV, electron beam, x-ray, excimer laserlight, γ-ray, synchrotron radiation or vacuum UV (soft x-ray), directlyor through a mask. The exposure dose is preferably about 1 to 200mJ/cm², more preferably about 10 to 100 mJ/cm², or 0.1 to 100 μC/cm²,more preferably 0.5 to 50 μC/cm². The resist film is further baked (PEB)on a hot plate at 60 to 150° C. for 10 seconds to 30 minutes, preferably80 to 120° C. for 30 seconds to 20 minutes.

Thereafter the resist film is developed with a developer in the form ofan aqueous base solution for 3 seconds to 3 minutes, preferably 5seconds to 2 minutes by conventional techniques such as dip, puddle orspray techniques. Suitable developers are 0.1 to 10 wt %, preferably 2to 10 wt %, more preferably 2 to 8 wt % aqueous solutions oftetramethylammonium hydroxide (TMAH), tetraethylammonium hydroxide(TEAH), tetrapropylammonium hydroxide (TPAH) and tetrabutylammoniumhydroxide (TBAH). The resist film in the exposed area is dissolved inthe developer whereas the resist film in the unexposed area is notdissolved. In this way, the desired positive pattern is formed on thesubstrate. It is appreciated that the resist composition of theinvention is best suited for micro-patterning using such high-energyradiation as EB, extreme UV (soft x-ray), x-ray, γ-ray and synchrotronradiation among others.

Although TMAH aqueous solution is generally used as the developer, TEAH,TPAH and TBAH having a longer alkyl chain are effective in inhibitingthe resist film from being swollen during development and thuspreventing pattern collapse. JP 3429592 describes an example using anaqueous TBAH solution for the development of a polymer comprisingrecurring units having an alicyclic structure such as adamantanemethacrylate and recurring units having an acid labile group such ast-butyl methacrylate, the polymer being water repellent due to theabsence of hydrophilic groups.

The TMAH developer is most often used as 2.38 wt % aqueous solution,which corresponds to 0.26N. The TEAH, TPAH, and TBAH aqueous solutionsshould preferably have an equivalent normality. The concentration ofTEAH, TPAH, and TBAH that corresponds to 0.26N is 3.84 wt %, 5.31 wt %,and 6.78 wt %, respectively.

When a pattern with a line size of 32 nm or less is resolved by the EBand EUV lithography, there arises a phenomenon that lines become wavy,lines merge together, and merged lines collapse. It is believed thatthis phenomenon occurs because lines are swollen in the developer andthe thus expanded lines merge together. Since the swollen linescontaining liquid developer are as soft as sponge, they readily collapseunder the stress of rinsing. For this reason, the developer using along-chain alkyl developing agent is effective for preventing film swelland hence, pattern collapse.

Example

Synthesis Examples, Comparative Synthesis Examples, Examples andComparative Examples are given below for further illustrating theinvention, but they should not be construed as limiting the inventionthereto. Mw is a weight average molecular weight as measured by gelpermeation chromatography (GPC) versus polystyrene standards usingtetrahydrofuran as a solvent, and Mw/Mn designates molecular weightdistribution or dispersity. All parts (pbw) are by weight.

Monomer Synthesis

Polymerizable acid-labile compounds within the scope of the inventionwere synthesized as follows.

Monomer Synthesis Example 1 Synthesis of6,7,8,9-tetrahydro-5H-benzocyclohepten-5-yl methacrylate (Monomer 1)

With stirring and ice cooling, 111 g of triethylamine was added to amixture of 120 g of methacrylic acid chloride, 240 g of6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol, and 1500 g of toluene. Themixture was stirred at room temperature for 16 hours. By standardaqueous work-up and solvent distillation, a crude product was obtained.It was purified by column chromatography, yielding the target compound,6,7,8,9-tetrahydro-5H-benzocyclohepten-5-yl methacrylate.

By the same procedure, Monomers 2 to 12 were synthesized. In thesynthesis of Monomers 5 to 9, the reactant6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol was replaced by2,3-dihydro-2,2-dimethyl-1H-inden-1-ol for Monomer 5,1,2,3,4-tetrahydro-2,2-dimethylnaphthalen-1-ol for Monomer 6,5,6,7,8,9,10-hexahydrobenzo-8H-cycloocten-5-ol for Monomer 7,5,6,7,8,9,10-hexahydrobenzo-8H-cyclooctene-5-methyl-5-ol for Monomer 8,and 5,6,7,8,9,10-hexahydrobenzo-8H-cyclooctene-5-vinyl-5-ol for Monomer9.

In the synthesis of Monomers 2 to 4, the reaction was replaced by

reaction of 6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol with4-oxatricyclo[4.2.1.0^(3,7)]nonan-5-on-2-yl methacrylicacid-5-carboxylic acid for Monomer 2,reaction of 6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol with4-vinylbenzoic acid for Monomer 3, andreaction of 6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol with5-vinyl-1-naphthoic acid for Monomer 4.

In the synthesis of Monomers 10 to 12, the reactant6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol was replaced by1,2,3,4-tetrahydro-2-methylnaphthalene-1-ol for monomer 10,1,2,3,4-tetrahydro-2-ethylnaphthalene-1-ol for monomer 11,1,2,3,4-tetrahydro-4-methylnaphthalene-1-ol for monomer 12.

Monomer 1: 6,7,8,9-tetrahydro-5H-benzocyclohepten-5-yl methacrylate

Monomer 2:9-(6,7,8,9-tetrahydro-5H-benzocyclohepten-5-yloxycarbonyl)-4-oxatricyclo[4.2.1.0^(3,7)]nonan-5-on-2-ylmethacrylate

Monomer 3: 6,7,8,9-tetrahydro-5H-benzocyclohepten-5-yl 4-vinylbenzoate

Monomer 4: 6,7,8,9-tetrahydro-5H-benzocyclohepten-5-yl5-vinyl-1-naphthoate

Monomer 5: 2,2-dimethyl-1-indanyl methacrylate

Monomer 6: 1,2,3,4-tetrahydro-2,2-dimethylnaphthalen-1-yl methacrylate

Monomer 7: 5,6,7,8,9,10-hexahydrobenzocycloocten-5-yl methacrylate

Monomer 8: 6,7,8,9-tetrahydro-5H-benzocycloheptene-5-methyl-5-ylmethacrylate

Monomer 9: 6,7,8,9-tetrahydro-5H-benzocycloheptene-5-vinyl-5-ylmethacrylate

Monomer 10:1,2,3,4-tetrahydro-2-methylnaphthalen-1-yl methacrylate

Monomer 11: 1,2,3,4-tetrahydro-2-ethylnaphthalen-1-yl methacrylate

Monomer 12: 1,2,3,4-tetrahydro-4-methylnaphthalen-1-yl methacrylate

PAG monomers 1 to 3 and Adhesive monomers 1 and 2 used herein are shownbelow.

-   PAG monomer 1: 4-methacrylic acid-oxyphenyldiphenylsulfonium    perfluorobutanesulfonate-   PAG monomer 2: triphenylsulfonium    2,3,5,6-tetrafluoro-4-methacryloyloxybenzenesulfonate-   PAG monomer 3: triphenylsulfonium    1,1,3,3,3-pentafluoro-2-methacryloyloxypropane-1-sulfonate

-   Adhesive monomer 1: 2-oxo-1,3-benzoxathiol-5-yl methacrylate-   Adhesive monomer 2: 2-oxo-2,3-dihydrobenzoxazol-5-yl methacrylate

Polymer Synthesis Polymer Synthesis Example 1

A 2-L flask was charged with 4.6 g of Monomer 1, 13.0 g of4-acetoxystyrene, and 40 g of tetrahydrofuran as solvent. The reactorwas cooled to −70° C. in a nitrogen atmosphere, whereupon vacuumevacuation and nitrogen blow were repeated three times. The reactorwarmed up to room temperature whereupon 1.2 g of azobisisobutyronitrile(AIBN) was added as a polymerization initiator. The reactor was heatedat 60° C. and reaction run for 15 hours. The reaction solution wasprecipitated from 1 L of isopropyl alcohol. The white solid wascollected by filtration and dissolved again in a mixture of 100 mL ofmethanol and 200 mL of tetrahydrofuran, to which 10 g of triethylamineand 10 g of water were added. Deprotection reaction of acetyl group wasconducted at 70° C. for 5 hours, followed by neutralization with aceticacid. The reaction solution was concentrated and dissolved in 100 mL ofacetone. By similar precipitation, filtration, and drying at 60° C., awhite polymer was obtained.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxystyrene=0.20:0.80

-   -   Mw=8,600    -   Mw/Mn=1.79

This is designated Polymer 1.

Polymer Synthesis Example 2

A 2-L flask was charged with 4.1 g of Monomer 1, 14.5 g of3-hydroxyphenyl methacrylate, and 40 g of tetrahydrofuran as solvent.The reactor was cooled to −70° C. in a nitrogen atmosphere, whereuponvacuum evacuation and nitrogen blow were repeated three times. Thereactor warmed up to room temperature whereupon 1.2 g of AIBN was addedas a polymerization initiator. The reactor was heated at 60° C. andreaction run for 15 hours. The reaction solution was precipitated from 1L of isopropyl alcohol. The white solid was collected by filtration andvacuum dried at 60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 3-hydroxyphenyl methacrylate=0.18:0.82

-   -   Mw=8,300    -   Mw/Mn=1.96

This is designated Polymer 2.

Polymer Synthesis Example 3

A 2-L flask was charged with 4.1 g of Monomer 1, 17.9 g of5-hydroxyindan-2-yl methacrylate, and 40 g of tetrahydrofuran assolvent. The reactor was cooled to −70° C. in a nitrogen atmosphere,whereupon vacuum evacuation and nitrogen blow were repeated three times.The reactor warmed up to room temperature whereupon 1.2 g of AIBN wasadded as a polymerization initiator. The reactor was heated at 60° C.and reaction run for 15 hours. The reaction solution was precipitatedfrom 1 L of isopropyl alcohol. The white solid was collected byfiltration and vacuum dried at 60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 5-hydroxyindan-2-yl methacrylate=0.18:0.82

-   -   Mw=8,700    -   Mw/Mn=1.83

This is designated Polymer 3.

Polymer Synthesis Example 4

A 2-L flask was charged with 6.9 g of Monomer 1, 8.7 g of5-hydroxyindan-2-yl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, and 40 gof tetrahydrofuran as solvent. The reactor was cooled to −70° C. in anitrogen atmosphere, whereupon vacuum evacuation and nitrogen blow wererepeated three times. The reactor warmed up to room temperaturewhereupon 1.2 g of AIBN was added as a polymerization initiator. Thereactor was heated at 60° C. and reaction run for 15 hours. The reactionsolution was precipitated from 1 L of isopropyl alcohol. The white solidwas collected by filtration and vacuum dried at 60° C., obtaining awhite polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 5-hydroxyindan-2-yl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-ylmethacrylate=0.30:0.40:0.30

-   -   Mw=8,200    -   Mw/Mn=1.87

This is designated Polymer 4.

Polymer Synthesis Example 5

A 2-L flask was charged with 5.3 g of Monomer 1, 1.7 g of indene, 10.8 gof 4-acetoxystyrene, and 40 g of tetrahydrofuran as solvent. The reactorwas cooled to −70° C. in a nitrogen atmosphere, whereupon vacuumevacuation and nitrogen blow were repeated three times. The reactorwarmed up to room temperature whereupon 1.2 g of AIBN was added as apolymerization initiator. The reactor was heated at 60° C. and reactionrun for 15 hours. The reaction solution was precipitated from 1 L ofisopropyl alcohol. The white solid was collected by filtration anddissolved again in a mixture of 100 mL of methanol and 200 mL oftetrahydrofuran, to which 10 g of triethylamine and 10 g of water wereadded. Deprotection reaction of acetyl group was conducted at 70° C. for5 hours, followed by neutralization with acetic acid. The reactionsolution was concentrated and dissolved in 100 mL of acetone. By similarprecipitation, filtration, and drying at 60° C., a white polymer wasobtained.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: indene: 4-hydroxystyrene=0.23:0.10:0.67

-   -   Mw=8,500    -   Mw/Mn=1.77

This is designated Polymer 5.

Polymer Synthesis Example 6

A 2-L flask was charged with 6.4 g of Monomer 1, 5.3 g of4-hydroxyphenyl methacrylate, 6.8 g of 4-acetoxystyrene, and 40 g oftetrahydrofuran as solvent. The reactor was cooled to −70° C. in anitrogen atmosphere, whereupon vacuum evacuation and nitrogen blow wererepeated three times. The reactor warmed up to room temperaturewhereupon 1.2 g of AIBN was added as a polymerization initiator. Thereactor was heated at 60° C. and reaction run for 15 hours. The reactionsolution was precipitated from 1 L of isopropyl alcohol. The white solidwas collected by filtration and dissolved again in a mixture of 100 mLof methanol and 200 mL of tetrahydrofuran, to which 10 g oftriethylamine and 10 g of water were added. Deprotection reaction ofacetyl group was conducted at 70° C. for 5 hours, followed byneutralization with acetic acid. The reaction solution was concentratedand dissolved in 100 mL of acetone. By similar precipitation,filtration, and drying at 60° C., a white polymer was obtained.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxyphenyl methacrylate: 4-hydroxystyrene=0.28:0.30:0.42

-   -   Mw=7,100    -   Mw/Mn=1.65

This is designated Polymer 6.

Polymer Synthesis Example 7

A 2-L flask was charged with 6.0 g of Monomer 1, 6.8 g of1-hydroxynaphthalen-5-yl methacrylate, 7.5 g oftetrahydro-2-oxofuran-3-yl methacrylate, and 40 g of tetrahydrofuran assolvent. The reactor was cooled to −70° C. in a nitrogen atmosphere,whereupon vacuum evacuation and nitrogen blow were repeated three times.The reactor warmed up to room temperature whereupon 1.2 g of AIBN wasadded as a polymerization initiator. The reactor was heated at 60° C.and reaction run for 15 hours. The reaction solution was precipitatedfrom 1 L of isopropyl alcohol. The white solid was collected byfiltration and vacuum dried at 60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 1-hydroxynaphthalen-5-yl methacrylate:tetrahydro-2-oxofuran-3-yl methacrylate=0.26:0.30:0.44

-   -   Mw=7,900    -   Mw/Mn=1.93

This is designated Polymer 7.

Polymer Synthesis Example 8

A 2-L flask was charged with 5.3 g of Monomer 1, 10.7 g of4-acetoxystyrene, 1.7 g of acenaphthylene, and 20 g of tetrahydrofuranas solvent. The reactor was cooled to −70° C. in a nitrogen atmosphere,whereupon vacuum evacuation and nitrogen blow were repeated three times.The reactor warmed up to room temperature whereupon 1.2 g of AIBN wasadded as a polymerization initiator. The reactor was heated at 60° C.and reaction run for 15 hours. The reaction solution was precipitatedfrom 1 L of isopropyl alcohol. The white solid was collected byfiltration and dissolved again in a mixture of 100 mL of methanol and200 mL of tetrahydrofuran, to which 10 g of triethylamine and 10 g ofwater were added. Deprotection reaction of acetyl group was conducted at70° C. for 5 hours, followed by neutralization with acetic acid.

The reaction solution was concentrated and dissolved in 100 mL ofacetone. By similar precipitation, filtration, and drying at 60° C., awhite polymer was obtained.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxystyrene: acenaphthylene=0.23:0.67:0.10

-   -   Mw=6,100    -   Mw/Mn=1.79

This is designated Polymer 8.

Polymer Synthesis Example 9

A 2-L flask was charged with 5.5 g of Monomer 1, 2.0 g of7-acetoxyindene, 10.6 g of 4-acetoxystyrene, and 40 g of tetrahydrofuranas solvent. The reactor was cooled to −70° C. in a nitrogen atmosphere,whereupon vacuum evacuation and nitrogen blow were repeated three times.The reactor warmed up to room temperature whereupon 1.2 g of AIBN wasadded as a polymerization initiator. The reactor was heated at 60° C.and reaction run for 15 hours. The reaction solution was precipitatedfrom 1 L of isopropyl alcohol. The white solid was collected byfiltration and dissolved again in a mixture of 100 mL of methanol and200 mL of tetrahydrofuran, to which 10 g of triethylamine and 10 g ofwater were added. Deprotection reaction of acetyl group was conducted at70° C. for 5 hours, followed by neutralization with acetic acid. Thereaction solution was concentrated and dissolved in 100 mL of acetone.By similar precipitation, filtration, and drying at 60° C., a whitepolymer was obtained.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 7-hydroxyindene: 4-hydroxystyrene=0.24:0.10:0.66

-   -   Mw=6,300    -   Mw/Mn=1.75

This is designated Polymer 9.

Polymer Synthesis Example 10

A 2-L flask was charged with 5.3 g of Monomer 1, 8.3 g of4-acetoxystyrene, 2.7 g of 6-hydroxycoumarin, 1.5 g of coumarin, and 20g of tetrahydrofuran as solvent. The reactor was cooled to −70° C. in anitrogen atmosphere, whereupon vacuum evacuation and nitrogen blow wererepeated three times. The reactor warmed up to room temperaturewhereupon 1.2 g of AIBN was added as a polymerization initiator. Thereactor was heated at 60° C. and reaction run for 15 hours. The reactionsolution was precipitated from 1 L of isopropyl alcohol. The white solidwas collected by filtration and dissolved again in a mixture of 100 mLof methanol and 200 mL of tetrahydrofuran, to which 10 g oftriethylamine and 10 g of water were added. Deprotection reaction ofacetyl group was conducted at 70° C. for 5 hours, followed byneutralization with acetic acid. The reaction solution was concentratedand dissolved in 100 mL of acetone. By similar precipitation,filtration, and drying at 60° C., a white polymer was obtained.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxystyrene: 6-hydroxycoumarin:coumarin=0.23:0.52:0.15:0.10

-   -   Mw=6,900    -   Mw/Mn=1.79

This is designated Polymer 10.

Polymer Synthesis Example 11

A 2-L flask was charged with 5.3 g of Monomer 1, 15.5 g of5-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl methacrylate, 1.6 g ofchromone, and 20 g of tetrahydrofuran as solvent. The reactor was cooledto −70° C. in a nitrogen atmosphere, whereupon vacuum evacuation andnitrogen blow were repeated three times. The reactor warmed up to roomtemperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 5-hydroxy-1,2,3,4-tetrahydronaphthalen-2-yl methacrylate:chromone=0.23:0.67:0.10

-   -   Mw=6,600    -   Mw/Mn=1.83

This is designated Polymer 11.

Polymer Synthesis Example 12

A 2-L flask was charged with 6.7 g of Monomer 3, 10.7 g of4-acetoxystyrene, 1.6 g of chromone, and 20 g of tetrahydrofuran assolvent. The reactor was cooled to −70° C. in a nitrogen atmosphere,whereupon vacuum evacuation and nitrogen blow were repeated three times.The reactor warmed up to room temperature whereupon 1.2 g of AIBN wasadded as a polymerization initiator. The reactor was heated at 60° C.and reaction run for 15 hours. The reaction solution was precipitatedfrom 1 L of isopropyl alcohol. The white solid was collected byfiltration and dissolved again in a mixture of 100 mL of methanol and200 mL of tetrahydrofuran, to which 10 g of triethylamine and 10 g ofwater were added. Deprotection reaction of acetyl group was conducted at70° C. for 5 hours, followed by neutralization with acetic acid. Thereaction solution was concentrated and dissolved in 100 mL of acetone.By similar precipitation, filtration, and drying at 60° C., a whitepolymer was obtained.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 3: 4-hydroxystyrene: chromone=0.23:0.67:0.10

-   -   Mw=7,800    -   Mw/Mn=1.79

This is designated Polymer 12.

Polymer Synthesis Example 13

A 2-L flask was charged with 7.9 g of Monomer 4, 10.4 g of4-acetoxystyrene, 1.8 g of coumarin, and 20 g of tetrahydrofuran assolvent. The reactor was cooled to −70° C. in a nitrogen atmosphere,whereupon vacuum evacuation and nitrogen blow were repeated three times.The reactor warmed up to room temperature whereupon 1.2 g of AIBN wasadded as a polymerization initiator. The reactor was heated at 60° C.and reaction run for 15 hours. The reaction solution was precipitatedfrom 1 L of isopropyl alcohol. The white solid was collected byfiltration and dissolved again in a mixture of 100 mL of methanol and200 mL of tetrahydrofuran, to which 10 g of triethylamine and 10 g ofwater were added. Deprotection reaction of acetyl group was conducted at70° C. for 5 hours, followed by neutralization with acetic acid. Thereaction solution was concentrated and dissolved in 100 mL of acetone.By similar precipitation, filtration, and drying at 60° C., a whitepolymer was obtained.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 4: 4-hydroxystyrene: coumarin=0.23:0.65:0.12

-   -   Mw=7,900    -   Mw/Mn=1.96

This is designated Polymer 13.

Polymer Synthesis Example 14

A 2-L flask was charged with 6.9 g of Monomer 1, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 6.5 g ofPAG monomer 1, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 1=0.30:0.30:0.30:0.10

-   -   Mw=8,600    -   Mw/Mn=1.96

This is designated Polymer 14.

Polymer Synthesis Example 15

A 2-L flask was charged with 6.9 g of Monomer 1, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.7 g ofPAG monomer 2, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 2=0.30:0.30:0.30:0.10

-   -   Mw=8,900    -   Mw/Mn=1.99

This is designated Polymer 15.

Polymer Synthesis Example 16

A 2-L flask was charged with 8.3 g of Monomer 1, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.30:0.30:0.10

-   -   Mw=7,600    -   Mw/Mn=1.97

This is designated Polymer 16.

Polymer Synthesis Example 17

A 2-L flask was charged with 3.5 g of Monomer 1, 4.1 g of3-ethyl-3-exo-tetracyclo[4.4.0.1^(2,50).1^(7,10)]dodecanyl methacrylate,5.3 g of 4-hydroxyphenyl methacrylate, 6.5 g of2,7-dihydro-2-oxobenzo[C]furan-5-yl methacrylate, 5.6 g of PAG monomer3, and 40 g of tetrahydrofuran as solvent. The reactor was cooled to−70° C. in a nitrogen atmosphere, whereupon vacuum evacuation andnitrogen blow were repeated three times. The reactor warmed up to roomtemperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 3-ethyl-3-exo-tetracyclo[4.4.0.1^(2,5).1^(7,10)]-dodecanylmethacrylate: 4-hydroxyphenyl methacrylate:2,7-dihydro-2-oxobenzo[α]furan-5-yl methacrylate: PAG monomer3=0.15:0.15:0.30:0.30:0.10

-   -   Mw=7,700    -   Mw/Mn=1.79

This is designated Polymer 17.

Polymer Synthesis Example 18

A 2-L flask was charged with 6.9 g of Monomer 1, 6.4 g of6-acetoxy-2-vinylnaphthalene, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent.

The reactor was cooled to −70° C. in a nitrogen atmosphere, whereuponvacuum evacuation and nitrogen blow were repeated three times. Thereactor warmed up to room temperature whereupon 1.2 g of AIBN was addedas a polymerization initiator. The reactor was heated at 60° C. andreaction run for 15 hours. The reaction solution was precipitated from 1L of isopropyl alcohol. The white solid was collected by filtration anddissolved again in a mixture of 100 mL of methanol and 200 mL oftetrahydrofuran, to which 10 g of triethylamine and 10 g of water wereadded. Deprotection reaction of acetyl group was conducted at 70° C. for5 hours, followed by neutralization with acetic acid. The reactionsolution was concentrated and dissolved in 100 mL of acetone. By similarprecipitation, filtration, and drying at 60° C., a white polymer wasobtained. The polymer was analyzed by ¹³C-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 6-hydroxy-2-vinylnaphthalene:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.30:0.30:0.10

-   -   Mw=8,300    -   Mw/Mn=1.91

This is designated Polymer 18.

Polymer Synthesis Example 19

A 2-L flask was charged with 6.9 g of Monomer 1, 6.5 g of5-hydroxyindan-2-yl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 5-hydroxyindan-2-yl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0″]nonan-9-yl methacrylate: PAG monomer3=0.30:0.30:0.30:0.10

-   -   Mw=8,100    -   Mw/Mn=1.83

This is designated Polymer 19.

Polymer Synthesis Example 20

A 2-L flask was charged with 6.9 g of Monomer 1, 7.4 g of5,8-dihydroxy-1,2,3,4-tetrahydronaphthalen-2-yl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]-nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 5,8-dihydroxy-1,2,3,4-tetrahydronaphthalen-2-yl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]-nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.20:0.40:0.10

-   -   Mw=8,800    -   Mw/Mn=1.96

This is designated Polymer 20.

Polymer Synthesis Example 21

A 2-L flask was charged with 6.9 g of Monomer 1, 7.4 g of6-hydroxycoumarin-3-yl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 6-hydroxycoumarin-3-yl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.20:0.40:0.10

-   -   Mw=8,100    -   Mw/Mn=1.81

This is designated Polymer 21.

Polymer Synthesis Example 22

A 2-L flask was charged with 12.3 g of Monomer 2, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 2: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.30:0.30:0.10

-   -   Mw=8,900    -   Mw/Mn=1.93

This is designated Polymer 22.

Polymer Synthesis Example 23

A 2-L flask was charged with 6.9 g of Monomer 1, 4.5 g of4-hydroxy-1-naphthalene methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxy-1-naphthalene methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0″]nonan-9-yl methacrylate: PAG monomer3=0.30:0.20:0.40:0.10

-   -   Mw=7,300    -   Mw/Mn=1.73

This is designated Polymer 23.

Polymer Synthesis Example 24

A 2-L flask was charged with 6.9 g of Monomer 5, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 5: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0⁴⁸]nonan-9-yl methacrylate: PAG monomer3=0.30:0.30:0.30:0.10

-   -   Mw=7,700    -   Mw/Mn=1.97

This is designated Polymer 24.

Polymer Synthesis Example 25

A 2-L flask was charged with 7.3 g of Monomer 6, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 6: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.30:0.30:0.10

-   -   Mw=7,500    -   Mw/Mn=1.85

This is designated Polymer 25.

Polymer Synthesis Example 26

A 2-L flask was charged with 7.3 g of Monomer 7, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 7: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0″]nonan-9-yl methacrylate: PAG monomer3=0.30:0.30:0.30:0.10

-   -   Mw=7,300    -   Mw/Mn=1.83

This is designated Polymer 26.

Polymer Synthesis Example 27

A 2-L flask was charged with 6.9 g of Monomer 1, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of Adhesive monomer 1, 5.6 g of PAGmonomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxyphenyl methacrylate: Adhesive monomer 1: PAG monomer3=0.30:0.30:0.30:0.10

-   -   Mw=7,300    -   Mw/Mn=1.66

This is designated Polymer 27.

Polymer Synthesis Example 28

A 2-L flask was charged with 6.9 g of Monomer 1, 5.3 g of4-hydroxyphenyl methacrylate, 7.4 g of Adhesive monomer 2, 5.6 g of PAGmonomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 1: 4-hydroxyphenyl methacrylate: Adhesive monomer 2: PAG monomer3=0.30:0.30:0.30:0.10

-   -   Mw=7,900    -   Mw/Mn=1.71

This is designated Polymer 28.

Polymer Synthesis Example 29

A 2-L flask was charged with 4.3 g of Monomer 8, 14.5 g of4-hydroxyphenyl methacrylate, and 40 g of tetrahydrofuran as solvent.The reactor was cooled to −70° C. in a nitrogen atmosphere, whereuponvacuum evacuation and nitrogen blow were repeated three times. Thereactor warmed up to room temperature whereupon 1.2 g of AIBN was addedas a polymerization initiator. The reactor was heated at 60° C. andreaction run for 15 hours. The reaction solution was precipitated from 1L of isopropyl alcohol. The white solid was collected by filtration andvacuum dried at 60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 8: 4-hydroxyphenyl methacrylate=0.18:0.82

-   -   Mw=8,600    -   Mw/Mn=1.92

This is designated Polymer 29.

Polymer Synthesis Example 30

A 2-L flask was charged with 4.6 g of Monomer 9, 14.5 g of4-hydroxyphenyl methacrylate, and 40 g of tetrahydrofuran as solvent.The reactor was cooled to −70° C. in a nitrogen atmosphere, whereuponvacuum evacuation and nitrogen blow were repeated three times. Thereactor warmed up to room temperature whereupon 1.2 g of AIBN was addedas a polymerization initiator. The reactor was heated at 60° C. andreaction run for 15 hours. The reaction solution was precipitated from 1L of isopropyl alcohol. The white solid was collected by filtration andvacuum dried at 60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 9: 4-hydroxyphenyl methacrylate=0.18:0.82

-   -   Mw=8,300    -   Mw/Mn=1.90

This is designated Polymer 30.

Polymer Synthesis Example 31

A 2-L flask was charged with 6.9 g of Monomer 10, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 10: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.30:0.30:0.10

-   -   Mw=7,900    -   Mw/Mn=1.99

This is designated Polymer 31.

Polymer Synthesis Example 32

A 2-L flask was charged with 7.3 g of Monomer 11, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 11: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.30:0.30:0.10

-   -   Mw=8,300    -   Mw/Mn=1.85

This is designated Polymer 32.

Polymer Synthesis Example 33

A 2-L flask was charged with 6.9 g of Monomer 12, 5.3 g of4-hydroxyphenyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.6 g ofPAG monomer 3, and 40 g of tetrahydrofuran as solvent. The reactor wascooled to −70° C. in a nitrogen atmosphere, whereupon vacuum evacuationand nitrogen blow were repeated three times. The reactor warmed up toroom temperature whereupon 1.2 g of AIBN was added as a polymerizationinitiator. The reactor was heated at 60° C. and reaction run for 15hours. The reaction solution was precipitated from 1 L of isopropylalcohol. The white solid was collected by filtration and vacuum dried at60° C., obtaining a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with theanalytical data shown below.

Copolymer composition (molar ratio)

Monomer 12: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.30:0.30:0.10

-   -   Mw=9,100    -   Mw/Mn=1.93

This is designated Polymer 33.

Comparative Synthesis Example 1

A polymer was synthesized by the same procedure as above.

Copolymer composition (molar ratio)

hydroxystyrene: 1-ethylcyclopentyl methacrylate=0.70:0.30

-   -   Mw=9,300    -   Mw/Mn=1.86

This is designated Comparative Polymer 1.

Comparative Synthesis Example 2

A polymer was synthesized by the same procedure as above.

Copolymer composition (molar ratio)

hydroxystyrene: 1-ethyladamantyl methacrylate=0.77:0.23

-   -   Mw=8,100    -   Mw/Mn=1.96

This is designated Comparative Polymer 2.

Comparative Synthesis Example 3

A polymer was synthesized by the same procedure as above.

Copolymer composition (molar ratio)

hydroxystyrene: 1-ethylcyclopentyl methacrylate: indene=0.73:0.17:0.10

-   -   Mw=8,100    -   Mw/Mn=1.79

This is designated Comparative Polymer 3.

Comparative Synthesis Example 4

A polymer was synthesized by the same procedure as above.

Copolymer composition (molar ratio)

hydroxystyrene: 1-ethylcyclopentyl methacrylate:acenaphthylene=0.75:0.15:0.10

-   -   Mw=7,200    -   Mw/Mn=1.79

This is designated Comparative Polymer 4.

Comparative Synthesis Example 5

A polymer was synthesized by the same procedure as above.

Copolymer composition (molar ratio)

hydroxystyrene: tetrahydronaphthalen-1-yl methacrylate==0.70:0.30

-   -   Mw=7,200    -   Mw/Mn=1.71

This is designated Comparative Polymer 5.

Comparative Synthesis Example 6

A polymer was synthesized by the same procedure as above.

Copolymer composition (molar ratio) hydroxystyrene: indan-1-ylmethacrylate=0.70:0.30

-   -   Mw=7,300    -   Mw/Mn=1.79

This is designated Comparative Polymer 6.

Comparative Synthesis Example 7

A polymer was synthesized by the same procedure as above.

Copolymer composition (molar ratio)

1-ethylcyclopentyl methacrylate: 4-hydroxyphenyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate: PAGmonomer 3=0.30:0.30:0.30:0.10

-   -   Mw=7,900    -   Mw/Mn=1.89

This is designated Comparative Polymer 7.

Examples and Comparative Examples

Positive resist compositions were prepared by dissolving each of thepolymers synthesized above and selected components in a solvent inaccordance with the recipe shown in Tables 1 and 2, and filteringthrough a filter having a pore size of 0.2 μm. The solvent contained 100ppm of a surfactant FC-4430 (3M Sumitomo Co., Ltd.).

The components in Tables 1 and 2 are as identified below.

-   Polymers 1 to 33: polymers synthesized in Polymer Synthesis Examples    1 to 33

Comparative Polymers 1 to 7:

-   -   polymers synthesized in Comparative Synthesis Examples 1 to 7

-   Organic solvents: propylene glycol monomethyl ether acetate (PGMEA)

-   cyclohexanone (CyH)    Acid generators: PAG1 and PAG2    Basic compounds: Amine 1, Amine 2, and Amine 3    Dissolution regulators:    -   DRI1 and DRI2

The structural formulae of these components are shown below.

EB Writing Test

Positive resist compositions were prepared by dissolving each of thepolymers synthesized above and selected components in a solvent inaccordance with the recipe shown in Tables 1 and 2, and filteringthrough a filter having a pore size of 0.2 μm.

Using a coater/developer system Clean Track Mark 5 (Tokyo ElectronLtd.), the positive resist composition was spin coated onto a siliconsubstrate (diameter 6 inches, vapor primed with hexamethyldisilazane(HMDS) and pre-baked on a hot plate at 110° C. for 60 seconds to form aresist film of 100 nm thick. Using a system HL-800D (Hitachi Ltd.) at aHV voltage of 50 keV, the resist film was exposed imagewise to EB in avacuum chamber.

Using Clean Track Mark 5, immediately after the imagewise exposure, thewafer was baked (PEB) on a hot plate for 60 seconds and puddle developedin a 2.38 wt % TMAH aqueous solution for 30 seconds to form a positivepattern.

Resolution is a minimum size at the exposure dose (sensitivity) thatprovides a 1:1 resolution of a 120-nm line-and-space pattern. The 120-nmline-and-space pattern was measured for line width roughness (LWR) underSEM.

The resist composition is shown in Tables 1 and 2 together with thesensitivity and resolution of EB lithography.

TABLE 1 Acid Dissolution Organic PEB Polymer generator Base regulatorsolvent temperature Sensitivity Resolution LWR (pbw) (pbw) (pbw) (pbw)(pbw) (° C.) (μC/cm²) (nm) (nm) Polymer 1 PAG 2 Amine 1 — PGMEA 80 28 856.0 (100) (10) (0.4) (2,000) Polymer 2 PAG 2 Amine 1 — PGMEA 90 32 856.3 (100) (10) (0.4) (2,000) Polymer 3 PAG 2 Amine 1 — PGMEA 90 33 857.0 (100) (10) (0.4) (2,000) Polymer 4 PAG 2 Amine 1 — PGMEA 90 40 857.1 (100) (10) (0.4) (2,000) Polymer 5 PAG 1 Amine 1 — PGMEA 85 36 856.6 (100) (10) (0.4) (2,000) Polymer 6 PAG 1 Amine 1 — PGMEA 80 37 856.3 (100) (10) (0.4) (2,000) Polymer 7 PAG 1 Amine 1 — PGMEA 85 34 856.6 (100) (10) (0.4) (2,000) Polymer 8 PAG 1 Amine 1 — PGMEA 85 32 857.0 (100) (10) (0.4) (2,000) Polymer 9 PAG 1 Amine 1 — PGMEA 90 33 856.6 (100) (10) (0.4) (2,000) Polymer 10 PAG 1 Amine 1 — PGMEA 85 38 856.2 (100) (10) (0.4) (2,000) Polymer 11 PAG 1 Amine 1 — PGMEA 90 40 856.0 (100) (10) (0.4) (2,000) Polymer 12 PAG 2 Amine 1 — PGMEA 85 33 907.0 (100) (10) (0.4) (2,000) Polymer 13 PAG 1 Amine 1 — PGMEA 90 35 907.0 (100) (10) (0.4) (2,000) Polymer 14 — Amine 1 — PGMEA (500) 90 41 805.6 (100) (0.4) CyH (1,500) Polymer 15 — Amine 1 — PGMEA (500) 90 46 825.5 (100) (0.4) CyH (1,500) Polymer 16 — Amine 1 — PGMEA (500) 90 41 654.6 (100) (0.4) CyH (1,500) Polymer 17 — Amine 1 — PGMEA (500) 90 37 805.0 (100) (0.4) CyH (1,500) Polymer 18 — Amine 1 — PGMEA (500) 90 39 655.2 (100) (0.4) CyH (1,500) Polymer 19 — Amine 1 — PGMEA (500) 95 32 655.3 (100) (0.4) CyH (1,500) Polymer 20 — Amine 1 — PGMEA (500) 95 46 704.6 (100) (0.4) CyH (1,500) Polymer 21 — Amine 1 — PGMEA (500) 95 40 704.1 (100) (0.4) CyH (1,500) Polymer 22 — Amine 1 — PGMEA (500) 95 40 704.0 (100) (0.4) CyH (1,500) Polymer 23 — Amine 1 — PGMEA (500) 80 45 704.6 (100) (0.4) CyH (1,500) Polymer 24 — Amine 1 — PGMEA (500) 95 43 704.5 (100) (0.4) CyH (1,500) Polymer 25 — Amine 1 — PGMEA (500) 95 47 704.2 (100) (0.4) CyH (1,500) Polymer 26 — Amine 1 — PGMEA (500) 80 44 654.8 (100) (0.4) CyH (1,500)

TABLE 2 Acid Dissolution Organic PEB Polymer generator Base regulatorsolvent temperature Sensitivity Resolution LWR (pbw) (pbw) (pbw) (pbw)(pbw) (° C.) (μC/cm²) (nm) (nm) Polymer 27 — Amine 1 — PGMEA (500) 95 3665 4.5 (100) (0.4) CyH (1,500) Polymer 28 — Amine 1 — PGMEA (500) 95 4265 4.4 (100) (0.4) CyH (1,500) Polymer 16 — Amine 2 — PGMEA (500) 90 4475 4.4 (100) (0.4) CyH (1,500) Polymer 16 — Amine 3 — PGMEA (500) 90 4375 4.2 (100) (0.4) CyH (1,500) Polymer 16 — Amine 1 DRI 1 PGMEA (500) 8533 80 4.1 (100) (0.4) (10) CyH (1,500) Polymer 16 — Amine 1 DRI 2 PGMEA(500) 85 38 80 4.2 (100) (0.4) (10) CyH (1,500) Polymer 29 PAG 2 Amine 1— PGMEA 80 49 80 6.0 (100) (10) (0.4) (2,000) Polymer 30 PAG 2 Amine 1 —PGMEA 75 46 80 6.1 (100) (10) (0.4) (2,000) Polymer 31 — Amine 2 — PGMEA(500) 95 38 75 4.6 (100) (0.4) CyH (1,500) Polymer 32 — Amine 2 — PGMEA(500) 95 36 75 4.7 (100) (0.4) CyH (1,500) Polymer 33 — Amine 2 — PGMEA(500) 95 40 75 4.3 (100) (0.4) CyH (1,500) Comparative PAG 2 Amine 1 —PGMEA 90 22 110 7.2 Polymer 1 (10) (0.4) (2,000) (100) Comparative PAG 2Amine 1 — PGMEA 95 28 120 7.3 Polymer 2 (10) (0.4) (2,000) (100)Comparative PAG 2 Amine 1 — PGMEA 90 28 100 7.1 Polymer 3 (10) (0.4)(2,000) (100) Comparative PAG 2 Amine 1 — PGMEA 90 32 95 7.8 Polymer 4(10) (0.4) (2,000) (100) Comparative PAG 2 Amine 1 — PGMEA 90 32 95 7.7Polymer 5 (10) (0.4) (2,000) (100) Comparative PAG 2 Amine 1 — PGMEA 9030 95 7.9 Polymer 6 (10) (0.4) (2,000) (100) Comparative — Amine 1 —PGMEA (500) 90 42 80 5.3 Polymer 7 (0.4) CyH (1,500) (100)

Dry Etching Test

Each polymer, 2 g, was thoroughly dissolved in 10 g of cyclohexanone,and passed through a filter having a pore size of 0.2 μm, obtaining apolymer solution. The polymer solution was spin coated onto a siliconsubstrate and baked to form a polymer film of 300 nm thick. Using a dryetching instrument TE-8500P (Tokyo Electron Ltd.), the polymer film wasetched with CHF₃/CF₄ gas under the following conditions.

Chamber pressure 40.0 Pa

RF power 1000 W

Gap 9 mm

CHF₃ gas flow rate 30 ml/min

CF₄ gas flow rate 30 ml/min

Ar gas flow rate 100 ml/min

Time 60 sec

The difference in polymer film thickness before and after etching wasdetermined, from which an etching rate per minute was computed. Theresults are shown in Table 3. A smaller value of film thicknessdifference, i.e., a lower etching rate indicates better etchingresistance.

TABLE 3 CHF₃/CF₄ gas etching rate (nm/min) Polymer 1 97 2 105 3 103 4115 5 92 6 105 7 99 8 92 9 92 10 93 11 95 12 93 13 97 14 98 15 96 16 10317 98 18 95 19 98 20 101 21 102 22 103 23 95 24 99 25 101 26 98 27 96 2898 29 102 30 100 31 102 32 103 33 102 Comparative 1 122 Polymer 2 112 3108 4 102 5 100 6 103 7 111

It is evident from Tables 1 and 2 that the resist compositions using theinventive polymers show satisfactory resolution, sensitivity and edgeroughness. Although some polymers comprising an acid generator ofpolymer type copolymerized therein and having conventional acid labilegroups are drastically improved in resolution and edge roughnessproperties and sometimes superior to those polymers which do not containan acid generator of polymer type, but fall within the scope of theinvention, the polymers having acid labile groups within the scope ofthe invention and comprising an acid generator copolymerized thereinexhibit excellent resolution and minimized edge roughness owing to theirsynergy. These polymers have good dry etching resistance as demonstratedby a smaller difference in film thickness before and after etching inTable 3.

Japanese Patent Application No. 2010-002679 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A positive resist composition comprising as a base resin a polymerhaving carboxyl groups whose hydrogen is substituted by an acid labilegroup having the general formula (1):

wherein W is an ethylene, propylene, butylene or pentylene group whichbonds at opposite ends to carbon atoms C_(A) and C_(B); R¹ is hydrogenor a straight, branched or cyclic C₁-C₆ alkyl group, which bonds to acarbon atom in W, with the proviso that R¹ is not hydrogen when W isethylene or propylene; m is an integer of 1 to 4, with the proviso thatwhen m is 2 or more, R¹ may be the same or different and R¹ may bondtogether to form a C₃-C₉ ring with a carbon atom in W; R² is selectedfrom the class consisting of C₁-C₄ alkyl, alkoxy, alkanoyl,alkoxycarbonyl, hydroxyl, nitro, C₆-C₁₀aryl, halogen, and cyano; n is aninteger of 1 to 4; and R is hydrogen or a straight, branched or cyclicC₁-C₁₂ alkyl, C₂-C₁₂ alkenyl, C₂-C₁₂ alkynyl or C₆-C₁₀ aryl group whichmay have an oxygen or sulfur atom.
 2. The resist composition of claim 1,comprising as the base resin a polymer comprising recurring units (a) ofthe general formula (2), selected from (meth)acrylic acid andderivatives thereof, styrenecarboxylic acid, andvinylnaphthalenecarboxylic acid, each having substituted thereon an acidlabile group of formula (1), the polymer having a weight averagemolecular weight of 1,000 to 500,000,

wherein W, R¹, R², R, C_(A), C_(B), m, and n are as defined above, X¹ isa single bond, —C(═O)—O—R⁴—, phenylene or naphthylene group, R⁴ is astraight, branched or cyclic C₁-C₁₀ alkylene group which may have anester group, ether group or lactone ring, and R³ is hydrogen or methyl.3. The resist composition of claim 2 wherein said polymer is a copolymercomprising recurring units (a) of the general formula (2), selected from(meth)acrylic acid and derivatives thereof, styrenecarboxylic acid, andvinylnaphthalenecarboxylic acid, each having substituted thereon an acidlabile group of formula (1), and recurring units (b) having an adhesivegroup selected from the class consisting of hydroxyl, lactone, ether,ester, carbonyl, and cyano groups, molar fractions “a” and “b” of therespective units being in the range: 0<a<1.0, 0<b<1.0, and 0.05≦a+b≦1.0,the copolymer having a weight average molecular weight of 1,000 to500,000.
 4. The resist composition of claim 3 wherein the recurringunits (b) are recurring units having a phenolic hydroxyl group.
 5. Theresist composition of claim 4 wherein the recurring units having aphenolic hydroxyl group are selected from units (b1) to (b8) representedby the general formula (3):

wherein X² and X³ each are a single bond or —C(═O)—O—R⁶—, X⁴ and X⁵ eachare —C(═O)—O—R⁶—, R⁶ is a single bond or a straight, branched or cyclicC₁-C₁₀ alkylene group, R⁵ is each independently hydrogen or methyl, Y¹and Y² each are methylene or ethylene, Z is methylene, oxygen or sulfur,and p is 1 or
 2. 6. The resist composition of claim 3 wherein thecopolymer has further copolymerized therein recurring units selectedfrom units (c1) to (c5) of indene, acenaphthylene, chromone, coumarin,and norbornadiene, or derivatives thereof, represented by the generalformula (4):

wherein R⁹ to R¹³ are each independently selected from the classconsisting of hydrogen, C₁-C₃₀ alkyl, partially or entirelyhalo-substituted alkyl, alkoxy, alkanoyl or alkoxycarbonyl group, C₆-C₁₀aryl group, halogen, and 1,1,1,3,3,3-hexafluoro-2-propanol, and Z ismethylene, oxygen or sulfur.
 7. The resist composition of claim 3wherein the copolymer has further copolymerized therein units selectedfrom sulfonium salts (dl) to (d3) represented by the general formula(5):

wherein R²⁰, R²⁴, and R²⁸ each are hydrogen or methyl, R²¹ is a singlebond, phenylene, —O—R³³—, or —C(═O)—Y—R³³—, Y is oxygen or NH, R³³ is astraight, branched or cyclic C₁-C₆ alkylene group, alkenylene orphenylene group, which may contain a carbonyl, ester, ether or hydroxylgroup, R²², R²³, R²⁵, R²⁶, R²⁷, R²⁹, R³⁰, and R³¹ are each independentlya straight, branched or cyclic C₁-C₁₂ alkyl group which may contain acarbonyl, ester or ether group, or a C₆-C₁₂ aryl, C₇-C₂₀ aralkyl, orthiophenyl group, Z₀ is a single bond, methylene, ethylene, phenylene,fluorophenylene, —O—R³²—, or —C(═O)—Z₁—R³²—, Z₁ is oxygen or NH, R³² isa straight, branched or cyclic C₁-C₆ alkylene group, alkenylene orphenylene group, which may contain a carbonyl, ester, ether or hydroxylradical, M⁻ is a non-nucleophilic counter ion, d1, d2 and d3 are in therange of 0≦d1≦.3, 0≦d2≦0.3, 0≦d3≦0.3, and 0<d1+d2+d3≦0.3.
 8. The resistcomposition of claim 1, further comprising an organic solvent and anacid generator, the composition being a chemically amplified positiveresist composition.
 9. The resist composition of claim 8, furthercomprising a dissolution regulator.
 10. The resist composition of claim8, further comprising a basic compound and/or a surfactant as anadditive.
 11. A pattern forming process comprising the steps of applyingthe positive resist composition of claim 1 onto a substrate to form acoating, heat treating and exposing the coating to high-energyradiation, and developing the exposed coating with a developer.